This invention relates to a group supervision apparatus for an elevator which allots hall calls to the cages of the elevator.
In group-supervisory elevators, in each of which a plurality of elevator cages are supervised as one group, there is what is termed the `assignment system` wherein when a hall call has been registered, a cage most suited to respond to the hall call is selected and is assigned to the hall call.
The assignment system is usually so constructed that the predicted value of the waiting period of time (hereinbelow, this value shall be termed the `predicted waiting time`) of each hall call is calculated, that an assignment estimation value is obtained for each of the cage assignments from the predicted waiting time in accordance with a predetermined assignment estimation function so as to select the assignment estimation value which provides the most effective operation.
It has heretofore been common practice that the waiting times of hall calls and the like are actually measured in a building in which an elevator is operating so as to decide from the measured results whether the elevator is operating effectively. The most common approach is a decision which is based on the mean waiting time and the rate of occurrence of long waits (the proportion of hall calls having a waiting time of at least 60 seconds). As the mean waiting time is shorter and as the rate of occurrence of long waits is smaller, the elevator performs more effectively. Further, it is a recent trend that more importance is attached to the rate of occurrence of long waits than to the mean waiting time.
In some buildings (for example, a hotel and an office building, a riding time (time required for a person to reach a destination floor since getting on a cage), a service completion time (time required for the person to reach the destination floor since entering a hall), and the like, are handled as objects to-be-estimated in addition to the waiting time of the hall call.
In consideration of such performance criteria, various assignment systems have hitherto been proposed. The estimation functions in these assignment systems are often categorized in accordance with their characteristics and defined as follows:
(a) Estimation function intended to minimize the maximum value of the waiting time of hall calls.
This corresponds to, for example, a system described in Japanese Patent Application Laid-open No. 50-149041, wherein the longest predicted waiting time of an allotted hall call is evaluated for each of a plurality of cages, and a cage having a minimum waiting time is preferentially assigned.
(b) Estimation function intended to minimize the mean value of the waiting time of hall calls.
This corresponds to, for example, a system described in Japanese Patent Application Laid-open No. 51-23932, wherein the summation or mean value of the predicted waiting times of all allotted hall calls are obtained, and a cage with a minimum waiting time is assigned.
(c) Estimation function intended to concentrate the distribution of the waiting time of hall calls in a predetermined reference waiting time, namely, to minimize the variance of the waiting time.
This corresponds to, for example, a system described in Japanese Patent Application Publication No. 55-21709 (Japanese Patent Application Laid-open No. 52-18655), wherein the deviation between the predicted waiting time of a hall call and a preset reference waiting time is calculated, and a cage having a smaller deviation is preferentially assigned. In another system described in Japanese Patent Application Laid-open No. 57-51668, a predicted waiting time is weighted according to a function by which an assignment estimation value is minimized when the predicted waiting time is equal to a reference value, and a cage having a minimum assignment estimation value is assigned.
(d) Estimation function intended to minimize the mean value of the mental waiting time (which correspond to the degree of impatience) of passengers waiting in halls.
This corresponds to, for example, a system described in Japanese Patent Application Laid-open No. 53-55847, wherein the predicted waiting times of hall calls are weighted accordance with their duration (for example, a longer waiting time is weighted more), and a cage with a minimum summation or mean value is assigned.
In considering an assignment system adapted to reduce the rate of occurrence of long waits by allotting with the hall calls using the mean value of the waiting time as described in the prior-art assignment system (b), the variance thereof sometimes enlarges in spite of the diminished mean value, and it has been difficult to say that the rate of occurrence of long waits is always reduced. To the contrary, with the hall call allotment wherein the variance of the waiting time is diminished as in the prior-art assignment system (c), the mean value thereof sometimes enlarges in spite of the diminished variance, and it has also been difficult to say that the rate of occurrence of long waits is reduced. The same applies to the prior-art assignment systems (a) and (d). In conclusion, each of the priori-art assignment systems (a)-(d) controls the allotment of hall calls with emphasis taken only on one of factors determining the distribution of the waiting time, such as the maximum waiting time, the mean value and the variance, so that it has not always reduced the rate of occurrence of long waits.